From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BFA53C433F5 for ; Thu, 28 Oct 2021 21:36:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AB8BE610FD for ; Thu, 28 Oct 2021 21:36:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231431AbhJ1VjC (ORCPT ); Thu, 28 Oct 2021 17:39:02 -0400 Received: from mail.kernel.org ([198.145.29.99]:56112 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231445AbhJ1Vi6 (ORCPT ); Thu, 28 Oct 2021 17:38:58 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 18571610E7; Thu, 28 Oct 2021 21:36:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1635456991; bh=JirqGpfpO/qxbnSaugdDW0snCqT4yJU1fdf6OO76ogw=; h=Date:From:To:Subject:In-Reply-To:From; b=0NwSL3j0dMAyVzWv1O9sb9AlC9NOKG0rddvU+x36ION1TylEa6Cub4nlcdANOOe2R 0MRnnzm2vvI0lLtCndhT+MdAyhDqadG+pipJ4E34l1c2MCt9pdbcouEVkNi1PqKjv+ 839stn4Z8cM8reBABe5JKJMhL0Mm7pBywrR6YjWU= Date: Thu, 28 Oct 2021 14:36:30 -0700 From: Andrew Morton To: akpm@linux-foundation.org, andrea.righi@canonical.com, hughd@google.com, kirill.shutemov@linux.intel.com, linux-mm@kvack.org, mm-commits@vger.kernel.org, shy828301@gmail.com, songliubraving@fb.com, stable@vger.kernel.org, sunhao.th@gmail.com, torvalds@linux-foundation.org, willy@infradead.org Subject: [patch 09/11] mm: khugepaged: skip huge page collapse for special files Message-ID: <20211028213630.X6Y5NAeme%akpm@linux-foundation.org> In-Reply-To: <20211028143506.5f5d5e2cd1f768a1da864844@linux-foundation.org> User-Agent: s-nail v14.8.16 Precedence: bulk Reply-To: linux-kernel@vger.kernel.org List-ID: X-Mailing-List: mm-commits@vger.kernel.org From: Yang Shi Subject: mm: khugepaged: skip huge page collapse for special files The read-only THP for filesystems will collapse THP for files opened readonly and mapped with VM_EXEC. The intended usecase is to avoid TLB misses for large text segments. But it doesn't restrict the file types so a THP could be collapsed for a non-regular file, for example, block device, if it is opened readonly and mapped with EXEC permission. This may cause bugs, like [1] and [2]. This is definitely not the intended usecase, so just collapse THP for regular files in order to close the attack surface. [1] https://lore.kernel.org/lkml/CACkBjsYwLYLRmX8GpsDpMthagWOjWWrNxqY6ZLNQVr6yx+f5vA@mail.gmail.com/ [2] https://lore.kernel.org/linux-mm/000000000000c6a82505ce284e4c@google.com/ [shy828301@gmail.com: fix vm_file check] Link: https://lkml.kernel.org/r/CAHbLzkqTW9U3VvTu1Ki5v_cLRC9gHW+znBukg_ycergE0JWj-A@mail.gmail.com Link: https://lkml.kernel.org/r/20211027195221.3825-1-shy828301@gmail.com Fixes: 99cb0dbd47a1 ("mm,thp: add read-only THP support for (non-shmem) FS") Signed-off-by: Hugh Dickins Signed-off-by: Yang Shi Reported-by: Hao Sun Reported-by: syzbot+aae069be1de40fb11825@syzkaller.appspotmail.com Cc: Matthew Wilcox Cc: Kirill A. Shutemov Cc: Song Liu Cc: Andrea Righi Cc: Signed-off-by: Andrew Morton --- mm/khugepaged.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) --- a/mm/khugepaged.c~mm-khugepaged-skip-huge-page-collapse-for-special-files +++ a/mm/khugepaged.c @@ -445,22 +445,25 @@ static bool hugepage_vma_check(struct vm if (!transhuge_vma_enabled(vma, vm_flags)) return false; + if (vma->vm_file && !IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - + vma->vm_pgoff, HPAGE_PMD_NR)) + return false; + /* Enabled via shmem mount options or sysfs settings. */ - if (shmem_file(vma->vm_file) && shmem_huge_enabled(vma)) { - return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, - HPAGE_PMD_NR); - } + if (shmem_file(vma->vm_file)) + return shmem_huge_enabled(vma); /* THP settings require madvise. */ if (!(vm_flags & VM_HUGEPAGE) && !khugepaged_always()) return false; - /* Read-only file mappings need to be aligned for THP to work. */ + /* Only regular file is valid */ if (IS_ENABLED(CONFIG_READ_ONLY_THP_FOR_FS) && vma->vm_file && - !inode_is_open_for_write(vma->vm_file->f_inode) && (vm_flags & VM_EXEC)) { - return IS_ALIGNED((vma->vm_start >> PAGE_SHIFT) - vma->vm_pgoff, - HPAGE_PMD_NR); + struct inode *inode = vma->vm_file->f_inode; + + return !inode_is_open_for_write(inode) && + S_ISREG(inode->i_mode); } if (!vma->anon_vma || vma->vm_ops) _